A56.4Chlamydial infection of pharynx

A56.4 is the ICD-10-CM diagnosis code for chlamydial infection of pharynx. It belongs to category A56 (other sexually transmitted chlamydial diseases), block A50-A64 (infections with a predominantly sexual mode of transmission) and chapter 1 (certain infectious and parasitic diseases). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Within A56 (other sexually transmitted chlamydial diseases), A56.4 is specifically for chlamydial infection of pharynx. Related codes cover chlamydial infection of lower genitourinary tract (A56.0), chlamydial infection of pelviperitoneum and other genitourinary organs (A56.1), chlamydial infection of genitourinary tract, unspecified (A56.2), chlamydial infection of anus and rectum (A56.3) and sexually transmitted chlamydial infection of other sites (A56.8).

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 011 (Tracheostomy for Face, Mouth and Neck Diagnoses or Laryngectomy with MCC, relative weight 5.6154), DRG 012 (Tracheostomy for Face, Mouth and Neck Diagnoses or Laryngectomy with CC, relative weight 4.381), DRG 013 (Tracheostomy for Face, Mouth and Neck Diagnoses or Laryngectomy without CC/MCC, relative weight 2.7307), DRG 152 (Otitis Media and URI with MCC, relative weight 1.1151) and DRG 153 (Otitis Media and URI without MCC, relative weight 0.7421), in Pre-MDC and MDC 03 (Diseases and Disorders of the Ear, Nose, Mouth and Throat), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 099.51 (other venereal diseases due to chlamydia trachomatis, pharynx).